Deep submicron and NANO CMOS single photon photodetector pixel with event based circuits for readout data-rate reduction communication system

Abstract

An avalanche photodiode and a sensor array comprising an array of said avalanche photodiodes is disclosed. Then avalanche photodiode comprises a substrate of a first conductivity type; a first well of a second conductivity type formed within the substrate; a second well of the second conductivity type formed substantially overlying and extending into the first well; a heavily doped region of the first conductivity type formed substantially overlying and extending into the first well, the junction between the heavily doped region and the second well forming an avalanche multiplication region; a guard ring formed from a first conductivity material positioned substantially about the periphery of the multiplication region at least partially underlying the heavily doped region; and an outer well ring of the second conductivity type formed about the perimeter of the deep well and the guard ring. The sensor array comprises a plurality of pixel elements, each of the pixel elements being configured to operate on discrete value continuous time (DVCT) basis. Each of the pixel elements can include the avalanche photodiode previously described.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application claims the benefit of U.S. provisional patent application No. 60 / 918,268 filed Mar. 15, 2007, the disclosure of which is incorporated herein by reference in its entirety.FIELD OF THE INVENTION[0002]The present invention relates generally to sensor arrays, and more particularly to a deep submicron and nano CMOS-fabricated avalanche photodiode design and resulting pixel for incorporation into one and two dimensional sensor arrays.BACKGROUND OF THE INVENTION[0003]Optical sensors for extreme low-level light conditions can convert single photons into a measurable electrical signal. Single-photon detectors, as these sensors are called, can be employed in vision systems with 3D imaging and range capability, for sensing at night or in caves, for low data rate intra- and inter-platform communications, and for molecular sensing in bio-analytical fluorescence imaging. One of the first technologies in the prior art capable of sensing...

AI Technical Summary

Problems solved by technology

Unfortunately, PMTs are bulky, easily damaged, expensive, susceptible to magnetic fields, and require high voltages for operation.

The resulting arrays were limited in size to 32×32 pixels, and required significant post-processing to connect readout circuitry.

Unfortunately, commercially available SPADs manufactured using high voltage CMOS processes suffer from reliability issues that limit the technology to feature sizes that are not competitive with low-voltage deep submicron and nano CMOS.

This limits the ultimate density and usability of SPAD arrays manufactured using high voltage CMOS processes, to applications that do not require high quality or dense detector arrays.

Fabrication steps that work to guarantee high breakdown voltages and eliminate latch-up often introduce leakage problems at crucial device interfaces.

The high dark count is likely the result of using STI material to form a guard ring, which creates a poor material interface at a crucial location inside the device and fails to buffer the bottom corners of the multiplication region from undesirable edge effects.

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